This fixes the problem where the user disconnects a device, connects a
different one, and the library doesn't notice because opening the same
HID path worked fine. (see https://github.com/spesmilo/electrum/issues/4806 )
Previously if an import of a dependent module (usb1, hid) failed, import
of the whole transport module would fail. This was resolved by catching
ImportErrors in the all_transports method.
This had two drawbacks:
- if something other than ImportError happened - e.g., libusb would
raise OSError if it couldn't find libusb.so - all_transports would crash
anyway
- at the same time, if a legitimately needed dependency
(typing_extensions) was missing, this would be masked by the ImportError
handling.
Instead, we unconditionally import the modules, and inside each one,
wrap dependencies in a try-except.
As an added benefit, it is now possible to disable a transport just by
setting SomeTransport.ENABLED = False
move all methods that are still relevant to TrezorClient (originally
BaseClient)
modify ProtocolMixin to be a compatibility shim
modify BaseClient to be a compatibility shim with a proxy to original
actual TrezorClient - this prevents early failures in Electrum for long
enough to show an error message
Only a limited number of messages should be dispatched to handlers
that can be inserted anywhere in the protocol flow. Having a fixed list
of interjecting handlers makes this clearer and prevents hard-to-find
bugs.
remove Trezor 2 support from HID transport, which never worked
use ProtocolV1 explicitly everywhere, as V2 doesn't exist in practice
move USB IDs and UDEV warning string to a common place
fix a bug where HID would return a list instead of bytes
This fixes the breakage introduced by transport reshuffles.
It's still not great and I'd love to see context manager based sessions.
But it's good enough for now.
This commit breaks session handling (which matters with Bridge) and
regresses Bridge to an older code state. Both of these issues will be
rectified in subsequent commits.
Explanation of this big API reshuffle follows:
* protocols are moved to trezorlib.transport, and to a single common file.
* there is a cleaner definition of Transport and Protocol API (see below)
* fully valid mypy type hinting
* session handle counters and open handle counters mostly went away. Transports
and Protocols are meant to be "raw" APIs; TrezorClient will implement
context-handler-based sessions, session tracking, etc.
I'm calling this a "reshuffle" because it involved very small number of
code changes. Most of it is moving things around where they sit better.
The API changes are as follows.
Transport is now a thing that can:
* open and close sessions
* read and write protobuf messages
* enumerate and find devices
Some transports (all except bridge) are technically bytes-based and need
a separate protocol implementation (because we have two existing protocols,
although only the first one is actually used). Hence a protocol superclass.
Protocol is a thing that *also* can:
* open and close sessions
* read and write protobuf messages
For that, it requires a `handle`.
Handle is a physical layer for a protocol. It can:
* open and close some sort of device connection
(this is distinct from session! Connection is a channel over which you can
send data. Session is a logical arrangement on top of that; you can have
multiple sessions on a single connection.)
* read and write 64-byte chunks of data
With that, we introduce ProtocolBasedTransport, which simply delegates
the appropriate Transport functionality to respective Protocol methods.
hid and webusb transports are ProtocolBasedTransport-s that provide separate
device handles. HidHandle and WebUsbHandle existed before, but the distinction
of functionality between a Transport and its Handle was unclear. Some methods
were moved and now the handles implement the Handle API, while the transports
provide the enumeration parts of the Transport API, as well as glue between
the respective Protocols and Handles.
udp transport is also a ProtocolBasedTransport, but it acts as its own handle.
(That might be changed. For now, I went with the pre-existing structure.)
In addition, session_begin/end is renamed to begin/end_session to keep
consistent verb_noun naming.
